Mechanism of Electron-Induced Hydrogen Desorption from Hydroxylated Rutile TiO2 (110)

The mechanism of hydrogen desorption from rutile TiO2(110)-(1 x 1) was studied by injecting electrons with controlled energy and flux into single surface hydroxyls (OH) in cryogenic scanning tunneling microscopy (STM). Desorption proceeds without a clear threshold already at much lower energies than reported previously.(1) Our analysis identifies a transfer of H atoms from the TiO2 surface to the STM tip, triggered by vibrational heating due to inelastic electron tunneling, as the desorption mechanism. The reversible H-atom transfer between sample and tip can be used as a tool to discriminate OH from other surface species on TiO2 and to control the density and configuration of OH by selective removal and redeposition of H atoms on the oxide surface.